There is a widely-used machine tool by which a pallet, to which a work has been fixed, is detachably attached to a table or a pallet-mounting plate of a machine tool. The machine tool employs a pallet exchanger for exchanging a work that has not been machined with a work that has been machined. The pallet exchanger that has heretofore been generally used mounts new and old pallets on arms that extend horizontally in opposite directions about a vertical rotary shaft, and exchanges the pallets by changing over the positions of the new and old pallets by turning the rotary shaft by 180°.
The above pallet exchanger is so constituted as to horizontally support the pallets. There has further been proposed a pallet exchanger which holds the pallet in a vertical manner.
For example, International Publication WO 01/94071 discloses a pallet-mounting plate which is disposed to face the end of the main spindle and to rotate about a horizontal axis. This pallet-mounting plate has two pallet-mounting surfaces arranged back to back, and exchanges the new and old pallets by turning the pallet-mounting plate about the horizontal axis by 180°.
U.S. Patent Publication 5,172,464 discloses a pallet magazine in which a plurality of radial pallet holders are arranged maintaining an equal angular distance about the rotary shaft extending in the horizontal direction neighboring the machine tool, and a pallet is attached to each pallet holder for fixing a work to each pallet holder. One pallet vertically supported by the pallet magazine is exchanged between the magazine and a vertical table of the machine tool.
However, neither the International Publication WO 01/94071 nor U.S. Patent Publication 5,172,464 discloses a pallet exchanger which vertically attaches the pallets to both side surfaces of the pallet support member that rotates about the vertical axis.